water guage glass

[max corrigan]

i need to cut about 1/4" of a 3/16" glass tube as used in a boiler water level indicator anyone have any experience of this? the tube is so fragile i,m almost scared to touch it, (that's how i broke it in the first place) i have a diamond glass grinder which i think i might try in preference to cutting it,or is there a simpler way?
Regards Max..........

 

[Paolo]

I bought a piece of that tube in a chemistry shop...They told me..no prob for cutting ...just do a little indentation by the diamond glass grinder and, using a piece of rag, bent the tube in correspondence of it... and warm up the tip by a flame for levelling the cut...I confess you..never done yet...for the same reason's as you!!!
Cheers ;D

 

[steamer]

Hi,

I agree, the way I was shown, scribe a circle around the glass and wet the glass with water.

Then everything else Paolo said, especially the flame polish which I am told is important.

I hate gauge glass, I let glass cutters do it for me or by it precut......


Dave

 

[jack404]

I have a small diamond survival saw i have used this on bottles

wrap it around and go back and fourth untill its well marked

then a string soaked in metho spririts wrapped where the saw mark is .... light it..

then a ice cube rubbed on to put out the flame and create the tension on the glass

breaks on the line 60% of the time

best i can offer mate

jack

 

[gr8life]

Wonder if you can tell me how the glass is held in the fitting? Or where to find the answer. I am working off and on making a boiler, looked at the $$ of water level gauges and think I can make it from brass scrap. I just can't figure out how to seal the area where the glass & brass come together.
thanks
ed

 

[compound driver 2]

groove the glass with a three square diamond file, tap gently on a wooden surface and teh glass will brake at the line.
smooth over in a spirit flame holding the gauge glass in the flame just long enough for the surface to fuse.

Use a short length of silicone tube on each end of the gauge glass as a seal. do the top and bottom nuts up with your fingers and not a spanner. All you want is the silicone tube slightly crushed onto the body of the gauge and the glass of the tube.
BTW its Pyrex and not glass.

 

[max corrigan]

Wonder if you can tell me how the glass is held in the fitting? Or where to find the answer. I am working off and on making a boiler, looked at the $$ of water level gauges and think I can make it from brass scrap. I just can't figure out how to seal the area where the glass & brass come together.
thanks
ed

gr8life the glass in question is on a stuart boiler and their method of sealing is simply "o" rings they look like the ordinary ones to me,and then tightened up with the brass nuts! (that to me is where the problem lies)i think cd2 method might be the way to go, just pinch up finger tight, also pre-slip a piece of rod the same o/d as the glass through the two brass ends to make sure of correct alignment prior to inserting glass
hope this helps Max................

 

[tel]

A bit of teflon tape, twisted into a string and wound around the glass will do a much better job than either the silicon tube or the 'O' ring, and you can get your fittings down to a much more realistic scale size by using it

 

[compound driver 2]

Tel
teflon tape has no place on live steam especialy in the gauge glass. The silicone tube dosnt need much compression to make a good seal. The teflon will extrude out and can cause leaks. There was a guy scalded to death using PTFE its not good stuff in boiler use. Great on water pipes and low pressure/temperature applications.

I work on both scale and full size engines and PTFE is frowned on in both. Scale fittings can be made using the silicone tube method see the pictures of my last traction engine for details.

cheers Kevin

 

[tel]

Geez Kev, I must be like that bumblebee that can't (theoretically) fly then. I've been using it in gauge glasses and as gland packing for well over 20 years now with good results and no mishaps. The secret is to twist it into a string and then apply it as you would the graphited yarn. Extrusion generally occurs when you have (a) sloppy fits and (b) a bit of pipe on the handle of your of your spanner/wrench. Light pressure is the key - not much over finger tight for any fitting.

 

[DickDastardly40]

I once had to take 2" of several 5/8" dia glass tubes to bring them to the correct length for feed water tanks on one of my ships. We had about twice as many as were needed. When we only had what we needed plus one left, after trying various methods of cutting, I decided enough was enough. Fortunately we were alongside in Devonport in refit, so I took them up out of the dockyard to a glass shop and had them cut them for me. I never told my guys my secret method; whether they figured it out was not recorded!

Al

 

[compound driver 2]

Tel
Steam pressure will extrude PTFE from a joint with out any trouble. Even a good well made joint.
Its like the Bosswhite versis Foliac graphite argument, both work but one works a lot better.
With boilers I cant take chances im not keen on loosing my living and when driving a model traction engine my nuts (I never have anything between my legs that can blow up. Its been a life policy)

Cheers kevin

 

[Maryak]

I'm into leather when handling hot nuts : :

Regards
Bob

 

[max corrigan]

OK my orginal question was the best way to cut the glass is there such a thing as a fool proof way other than grinding? i have ordered from stuart's a new glass for a specific boiler! they will send two glasses of 3" long, which i need to cut down to
1" 5/8"(why they can't send the proper length i don't know ) other than they know you will screw up on the fitting and cutting of these glass tubes, which are extremeley (spelling) fragile
Max .............

 

[Maryak]

Max,

Apologies for the frivolity, packing materials to one side, the best way I know is:

1 Mark all the way around the glass with a glass cutter, diamond etc.

2. Soak a piece of natural fibre string in metholated spirit and tie this around the mark made in 1 above.

3. Set fire to the string.

4. If all has gone OK there should be a pop as the glass breaks at the mark.

5. Fuse the end in a flame.

Hope this helps.

Best Regards
Bob

 

[max corrigan]

Max,

Apologies for the frivolity, packing materials to one side, the best way I know is:

1 Mark all the way around the glass with a glass cutter, diamond etc.

2. Soak a piece of natural fibre string in metholated spirit and tie this around the mark made in 1 above.

3. Set fire to the string.

4. If all has gone OK there should be a pop as the glass breaks at the mark.

5. Fuse the end in a flame.

Hope this helps.

Best Regards
Bob

Bob i will let you know have not received glass from stuarts yet! afterwards i promise i will never touch a water glass again
many thanks Max........

 

[tel]

All I ever do is score around at the required point with a small triangular file and snap 'em off in my fingers. Then the flame polish, as others have said

 

[compound driver 2]

Tel
Whats the boiler in the picture used to provide steam for?

 

[tel]

Mostly stationary engines and any other steam gizmos. It's my 'shop' boiler - 5" dia with, from memory, about 25 1/2" fire tubes. Was originally coal fired, but I converted it to gas a couple of years back. I have had up to 125 psi in it, but the valves lift at 80 psi as most of my stuff runs at well and truly sub-100psi.